Partitioning: Initial suggestion

lib/data_layer.ex

@@ -252,6 +252,31 @@ defmodule AshPostgres.DataLayer do
     ]
   }
 
+  @partitioning %Spark.Dsl.Section{
+    name: :partitioning,
+    describe: """
+    A section for configuring the initial partitioning of the table
+    """,
+    examples: [
+      """
+      partitioning do
+        method :list
+        attribute :post
+      end
+      """
+    ],
+    schema: [
+      method: [
+        type: {:one_of, [:range, :list, :hash]},
+        doc: "Specifying what partitioning method to use"
+      ],
+      attribute: [
+        type: :atom,
+        doc: "The attribute to partition on"
+      ]
+    ]
+  }
+
   @postgres %Spark.Dsl.Section{
     name: :postgres,
     describe: """
@@ -262,7 +287,8 @@ defmodule AshPostgres.DataLayer do
       @custom_statements,
       @manage_tenant,
       @references,
-      @check_constraints
+      @check_constraints,
+      @partitioning
     ],
     modules: [
       :repo

lib/data_layer/info.ex

@@ -222,4 +222,14 @@ defmodule AshPostgres.DataLayer.Info do
   def manage_tenant_update?(resource) do
     Extension.get_opt(resource, [:postgres, :manage_tenant], :update?, false)
   end
+
+  @doc "Partitioning method"
+  def partitioning_method(resource) do
+    Extension.get_opt(resource, [:postgres, :partitioning], :method, nil)
+  end
+
+  @doc "Partitioning attribute"
+  def partitioning_attribute(resource) do
+    Extension.get_opt(resource, [:postgres, :partitioning], :attribute, nil)
+  end
 end

lib/migration_generator/migration_generator.ex

@@ -1367,7 +1367,8 @@ defmodule AshPostgres.MigrationGenerator do
              table: table,
              schema: schema,
              multitenancy: multitenancy,
-             repo: repo
+             repo: repo,
+             partitioning: partitioning
            }
            | rest
          ],
@@ -1376,7 +1377,12 @@ defmodule AshPostgres.MigrationGenerator do
        ) do
     group_into_phases(
       rest,
-      %Phase.Create{table: table, schema: schema, multitenancy: multitenancy, repo: repo},
+      %Phase.Create{
+        table: table,
+        schema: schema,
+        multitenancy: multitenancy, repo: repo,
+        partitioning: partitioning
+      },
       acc
     )
   end
@@ -2032,7 +2038,8 @@ defmodule AshPostgres.MigrationGenerator do
           schema: snapshot.schema,
           repo: snapshot.repo,
           multitenancy: snapshot.multitenancy,
-          old_multitenancy: empty_snapshot.multitenancy
+          old_multitenancy: empty_snapshot.multitenancy,
+          partitioning: snapshot.partitioning
         }
         | acc
       ])
@@ -3101,7 +3108,8 @@ defmodule AshPostgres.MigrationGenerator do
       repo: AshPostgres.DataLayer.Info.repo(resource, :mutate),
       multitenancy: multitenancy(resource),
       base_filter: AshPostgres.DataLayer.Info.base_filter_sql(resource),
-      has_create_action: has_create_action?(resource)
+      has_create_action: has_create_action?(resource),
+      partitioning: partitioning(resource)
     }
 
     hash =
@@ -3176,6 +3184,20 @@ defmodule AshPostgres.MigrationGenerator do
     end)
   end
 
+  defp partitioning(resource) do
+    method = AshPostgres.DataLayer.Info.partitioning_method(resource)
+    attribute = AshPostgres.DataLayer.Info.partitioning_attribute(resource)
+
+    if not is_nil(method) and not is_nil(attribute) do
+      %{
+        method: method,
+        attribute: attribute
+      }
+    else
+      nil
+    end
+  end
+
   defp multitenancy(resource) do
     strategy = Ash.Resource.Info.multitenancy_strategy(resource)
     attribute = Ash.Resource.Info.multitenancy_attribute(resource)

lib/migration_generator/operation.ex

@@ -145,7 +145,7 @@ defmodule AshPostgres.MigrationGenerator.Operation do
 
   defmodule CreateTable do
     @moduledoc false
-    defstruct [:table, :schema, :multitenancy, :old_multitenancy, :repo]
+    defstruct [:table, :schema, :multitenancy, :old_multitenancy, :repo, :partitioning]
   end
 
   defmodule AddAttribute do

lib/migration_generator/phase.ex

@@ -3,7 +3,15 @@ defmodule AshPostgres.MigrationGenerator.Phase do
 
   defmodule Create do
     @moduledoc false
-    defstruct [:table, :schema, :multitenancy, :repo, operations: [], commented?: false]
+    defstruct [
+      :table,
+      :schema,
+      :multitenancy,
+      :repo,
+      partitioning: nil,
+      operations: [],
+      commented?: false
+    ]
 
     import AshPostgres.MigrationGenerator.Operation.Helper, only: [as_atom: 1]
 
@@ -12,10 +20,13 @@ defmodule AshPostgres.MigrationGenerator.Phase do
           table: table,
           operations: operations,
           multitenancy: multitenancy,
-          repo: repo
+          repo: repo,
+          partitioning: partitioning
         }) do
       if multitenancy.strategy == :context do
-        "create table(:#{as_atom(table)}, primary_key: false, prefix: prefix()) do\n" <>
+        arguments = arguments([prefix(true), options(partitioning: partitioning)])
+
+        "create table(:#{as_atom(table)}, primary_key: false#{arguments}) do\n" <>
           Enum.map_join(operations, "\n", fn operation -> operation.__struct__.up(operation) end) <>
           "\nend"
       else
@@ -26,15 +37,10 @@ defmodule AshPostgres.MigrationGenerator.Phase do
             ""
           end
 
-        opts =
-          if schema do
-            ", prefix: \"#{schema}\""
-          else
-            ""
-          end
+        arguments = arguments([prefix(schema), options(partitioning: partitioning)])
 
         pre_create <>
-          "create table(:#{as_atom(table)}, primary_key: false#{opts}) do\n" <>
+          "create table(:#{as_atom(table)}, primary_key: false#{arguments}) do\n" <>
           Enum.map_join(operations, "\n", fn operation -> operation.__struct__.up(operation) end) <>
           "\nend"
       end
@@ -54,6 +60,28 @@ defmodule AshPostgres.MigrationGenerator.Phase do
         "drop table(:#{as_atom(table)}#{opts})"
       end
     end
+
+    def arguments([nil, nil]), do: ""
+    def arguments(arguments), do: ", " <> Enum.join(Enum.reject(arguments, &is_nil(&1)), ",")
+
+    def prefix(true), do: "prefix: prefix()"
+    def prefix(schema) when is_binary(schema) and schema != "", do: "prefix: \"#{schema}\""
+    def prefix(_), do: nil
+
+    def options(_options, _acc \\ [])
+    def options([], []), do: nil
+    def options([], acc), do: "options: \"#{Enum.join(acc, " ")}\""
+
+    def options([{:partitioning, %{method: method, attribute: attribute}} | rest], acc) do
+      option = "PARTITION BY #{String.upcase(Atom.to_string(method))} (#{attribute})"
+
+      rest
+      |> options(acc ++ [option])
+    end
+
+    def options([_ | rest], acc) do
+      options(rest, acc)
+    end
   end
 
   defmodule Alter do

lib/partitioning.ex

@@ -0,0 +1,114 @@
+defmodule AshPostgres.Partitioning do
+  @moduledoc false
+
+  @doc """
+  Create a new partition for a resource
+  """
+  def create_partition(resource, opts) do
+    repo = AshPostgres.DataLayer.Info.repo(resource)
+
+    resource
+    |> AshPostgres.DataLayer.Info.partitioning_method()
+    |> case do
+      :range ->
+        create_range_partition(repo, resource, opts)
+
+      :list ->
+        create_list_partition(repo, resource, opts)
+
+      :hash ->
+        create_hash_partition(repo, resource, opts)
+
+      unsupported_method ->
+        raise "Invalid partition method, got: #{unsupported_method}"
+    end
+  end
+
+  @doc """
+  Check if partition exists
+  """
+  def existing_partition?(resource, opts) do
+    repo = AshPostgres.DataLayer.Info.repo(resource)
+
+    resource
+    |> AshPostgres.DataLayer.Info.partitioning_method()
+    |> case do
+      :range ->
+        false
+
+      :list ->
+        partition_name = partition_name(resource, opts)
+        schema_exists?(repo, resource, partition_name, opts)
+
+      :hash ->
+        false
+
+      unsupported_method ->
+        raise "Invalid partition method, got: #{unsupported_method}"
+    end
+  end
+
+  # TBI
+  defp create_range_partition(_repo, _resource, _opts) do
+  end
+
+  defp create_list_partition(repo, resource, opts) do
+    key = Keyword.fetch!(opts, :key)
+    table = AshPostgres.DataLayer.Info.table(resource)
+    partition_name = partition_name(resource, opts)
+
+    schema =
+      Keyword.get(opts, :tenant)
+      |> tenant_schema(resource)
+
+    if schema_exists?(repo, resource, partition_name, opts) do
+      {:error, :already_exists}
+    else
+      Ecto.Adapters.SQL.query(
+        repo,
+        "CREATE TABLE \"#{schema}\".\"#{partition_name}\" PARTITION OF \"#{schema}\".\"#{table}\" FOR VALUES IN ('#{key}')"
+      )
+
+      if schema_exists?(repo, resource, partition_name, opts) do
+        :ok
+      else
+        {:error, "Unable to create partition"}
+      end
+    end
+  end
+
+  # TBI
+  defp create_hash_partition(_repo, _resource, _opts) do
+  end
+
+  defp schema_exists?(repo, resource, parition_name, opts) do
+    schema =
+      Keyword.get(opts, :tenant)
+      |> tenant_schema(resource)
+
+    %Postgrex.Result{} =
+      result =
+      repo
+      |> Ecto.Adapters.SQL.query!(
+        "select table_name from information_schema.tables t where t.table_schema = $1 and t.table_name = $2",
+        [schema, parition_name]
+      )
+
+    result.num_rows > 0
+  end
+
+  defp partition_name(resource, opts) do
+    key = Keyword.fetch!(opts, :key)
+    table = AshPostgres.DataLayer.Info.table(resource)
+    "#{table}_#{key}"
+  end
+
+  defp tenant_schema(tenant, resource) do
+    tenant
+    |> Ash.ToTenant.to_tenant(resource)
+    |> case do
+      nil -> "public"
+      tenant -> tenant
+    end
+  end
+end

priv/resource_snapshots/test_repo/partitioned_posts/20250214114101.json

@@ -0,0 +1,43 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"gen_random_uuid()\")",
+      "generated?": false,
+      "primary_key?": true,
+      "references": null,
+      "size": null,
+      "source": "id",
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": false,
+      "default": "1",
+      "generated?": false,
+      "primary_key?": true,
+      "references": null,
+      "size": null,
+      "source": "key",
+      "type": "bigint"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "custom_indexes": [],
+  "custom_statements": [],
+  "has_create_action": false,
+  "hash": "7FE5D9659135887A47FAE2729CEB0281FA8FF392EDB3B43426EAFD89A1518FEB",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "partitioning": {
+    "attribute": "key",
+    "method": "list"
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "schema": null,
+  "table": "partitioned_posts"
+}